The following is based on Korean Patent Application No. 99-43481 filed Oct. 8, 1999, herein incorporated by reference.
1. Field of the Invention
The present invention relates to an image processing apparatus and more particularly, to a method and apparatus for generating white color component and controlling the brightness in display devices.
2. Description of the Related Art
In a color display monitor or a color television, if a flat-panel display or color wheel filter is used, it is easier to increase the screen size, but the brightness of output image is deteriorated in comparison with use of a cathode-ray tube. To overcome such a drawback, a four-color output system in which white color component is added to the three primary colors of RGB (Red, Green, and Blue) is employed. The white component can be obtained by having a white light transmitted or reflected onto a white filter, which increases the overall brightness of the screen in display system. Therefore, what is needed is a method for extracting the white component from the RGB three primary colors to form the four primary color signals.
In an effort to increase the luminance of output image, a conventional method for using white filter in addition to RGB three color filters has been proposed by US-based Texas Instruments Inc., (U.S. Pat. No. 5,233,385). This method adopts a field-sequential way in which a white filter field or white frame is added by spatially or temporally dividing a color wheel or a video frame into four regions. As a result, the luminance of the output image can be increased in proportion to the size of the white field in image output systems. Such increase in luminance, however, signifies the increase of an achromatic color component, which causes color saturation of picture elements or pixels of an image to be reduced.
Another conventional method therefor has been presented by Japan-based Canon K.K., (U.S. Pat. No. 5,929,843). This method implemented by a binary liquid-crystal display includes the steps of extracting white component data from R, G, B color data, performing a pseudo half-tone process on the white component, and transmitting the suppressed white component to the display dot of RGB and White, in which case Red, Green, Blue and White are pixel units. The main feature of this method is in the non-linear conversion of the minimum value with the white component data obtained among the R, G, B color data, where non-linear models are gamma, offset, and scale. The above method contributes to turning the previous field-sequential based white color supplement into a pixel unit while adjusting the applied amount of white component depending upon a preset model. However, it raises a problem in that a decrease in color saturation with addition of white color fails to be noticed.
To solve the above problem, it is an objective of the present invention to provide a method and apparatus for converting a predetermined color signal into one including white signal.
It is another objective to provide a method and apparatus for increasing the brightness of an image without deteriorating color saturation.
Accordingly, to achieve the above objective of the invention, there is provided a method for generating a white signal component from a color signal including the steps of: calculating increases in the brightness of the primary color components constituting the color signal on the basis of each color component; extracting an increase in the white signal component from the brightness increases of the primary color components; and setting the increase in the white signal component as the white signal component of the color signal.
Where the color signal is comprised of Red, Green, Blue three-color signals, b1 is a predetermined constant indicative of scale, Brt is the increase in the brightness of an achromatic color depending upon input data, Ri, Gi, and Bi are vectors of the three primary color components, and       M1    =                            (                                    Ri              ·              Ri                        +                          Gi              ·              Gi                        +                          Bi              ·              Bi                                )                2              ,
in the step of calculating the brightness increases of the primary color components constituting the color signal on the basis of each color component, it is preferable to determine vR, vG, and vB, indicative of the respective increases of the brightness in red, green, and blue components of the color signal, as vR=b1*Brt*Ri/M1, vG=b1*Brt*Gi/M1, vB=b1*Brt*Bi/M1, respectively.
Furthermore, where the color signal is comprised of the three colors such as Red, Green and Blue, vR, vG and vB are the respective brightness increases of Red, Green and Blue primary color components, and cl is a predetermined constant indicative of scale, in the step of extracting an increase in the white signal component, it is preferable to determine such increase W as the result of multiplying the constant cl by the lowest value among the brightness increases of the primary colors.
On top of that, where the color signal is comprised of the three colors such as Red, Green and Blue, vR, vG and vB, respectively, are the brightnesses of Red, Green and Blue primary color components, and b1, b2 and b3 are predetermined constants, it is preferable to determine such increase W as W=B1*vR+b2*vG+b3*vB in the step of extracting an increase in the white signal component.
To achieve the above objective of the invention, there is also provided an apparatus for generating a white signal component from a color signal including: a primary color component brightness increase arithmetic unit for calculating the brightness increases of the primary color components constituting the color signal on the basis of each color component; a white signal increase arithmetic unit for extracting an increase in the white signal component from the brightness increases of the primary color components; and a signal applying unit for setting the increase of the white signal component as the white signal component of the color signal.
Where the color signal is comprised of Red, Green, Blue three-color signals, b1 is a predetermined constant indicative of scale, Brt is the brightness increase of an achromatic color depending upon input data, Ri, Gi, and Bi are vectors of the three primary color components of the color signal, and       M1    =                            (                                    Ri              ·              Ri                        +                          Gi              ·              Gi                        +                          Bi              ·              Bi                                )                2              ,
it is preferable to have the primary color component brightness increase arithmetic unit determine vR, vG, and vB which are the respective increases of the brightness in red, green, and blue components of the color signal as vR=b1*Brt*Ri/M1, vG=b1*Brt*Gi/M1, vB=b1*Brt*Bi/M1, respectively.
Furthermore, where the color signal is comprised of the three colors such as Red, Green and Blue, vR, vG and vB are the respective increases in the brightnesses of Red, Green and Blue primary color components, and c1 is the predetermined constant indicative of scale, it is preferable to have the white signal increase arithmetic unit determine the white signal increase W as the value multiplying the constant cl by the lowest value among the primary color brightness increases.
On top of that, where the color signal is comprised of the three colors such as Red, Green and Blue, vR, vG and vB are the respective increases in the brightnesses of Red, Green and Blue primary color components, and b1, b2 and b3 are predetermined constants, it is preferable to have the white signal increase arithmetic unit determine such increase W as W=b1*vR+b2*vG+b3*vB.
To achieve another objective of the invention, there is provided a method for controlling the brightness of an image including the steps of: calculating increases of primary color components constituting the image color signal on the basis of each primary color component to generate an increase in the white signal of the color signal; calculating brightness control components of the image by using the brightness increase of each primary color component and the increase of the white signal; and adding the image brightness control components to the image color signal to generate a brightness controlled image.
Where the color signal of the image is comprised of Red, Green, Blue three-color signals, b1 is a predetermined constant indicative of scale, Brt is the brightness increase of an achromatic color depending upon input data, Ri, Gi, and Bi are vectors of the three primary color components, and       M1    =                            (                                    Ri              ·              Ri                        +                          Gi              ·              Gi                        +                          Bi              ·              Bi                                )                2              ,
in the step of calculating the increase of the white signal, it is preferable to determine vR, vG, and vB, indicative of the respective brightness increases of red, green, and blue components of the color signal, as vR=b1*Brt*RI/M1, vG=b1*Brt* Gi/M1, vB=b1*Bit*Bi/M1, respectively.
Furthermore, where c1 is a predetermined constant indicative of scale, it is preferable to determine such increase W as the result of multiplying the constant c1 by the lowest value among the brightness increases of the primary colors, and where b2 and b3 are predetermined constants, it is preferable to determine such increase W as W=b1*vR+b2*vG+b3*vB.
Where the image color signal is comprised of three primary colors such as Red, Green and Blue, vR, vG, vB, and W are the respective brightness increases of Red, Green, Blue and White obtained from the step of generating the increase of the white component of the color signal, in the step of calculating the brightness control component of the image, it is preferable to determine Inc_R, Inc_G, and Inc_B which are the brightness control components of the primary colors Red, Green and Blue as Inc_R=vRxe2x88x92W, Inc_G=vGxe2x88x92W, Inc_B vBxe2x88x92W, respectively.
Further, where the image color signal is comprised of three colors such as Red, Green and Blue, Ri, Gi, and Bi are the respective vectors of the three primary color components, Inc_R, Inc_G, and Inc_B are the respective brightness control components of the primary colors Red, Green and Blue, and d1, d2 and d3 are predetermined constants, in the step of generating a brightness-controlled image, it is preferable to determine the primary color signal of the brightness-controlled output Ro, Go and Bo as Ro=Ri+d1*Inc_R, Go=Gi+d2*Inc_G, Bo=Bi+d3*Inc_B, respectively.
To achieve another objective of the invention, there is also provided an apparatus for controlling the brightness of an image including: a color signal brightness increase arithmetic unit for calculating brightness increases of primary color component constituting the image color signal on the basis of each primary color component to generate an increase in the white signal of the color signal; an image brightness control arithmetic unit for calculating the image brightness control components using the brightness increases of each primary color component and the white signal; and a control signal generator for adding the image brightness control component to the image color signal to generate a brightness controlled image.
Where the image color signal is comprised of three primary colors such as Red, Green and Blue, vR, vG, vB, and W are the respective brightness increases of Red, Green, Blue and White, which are obtained from the image color signal brightness increase arithmetic unit, it is preferable to have the image brightness control arithmetic unit determine Inc_R, Inc_G, and Inc_B indicative of the brightness control components of the primary colors Red, Green and Blue as Inc_R=vR-W, Inc_G=vG-W, Inc_B=vB-W, respectively.
Further, where the image color signal is comprised of three colors such as Red, Green and Blue, Ri, Gi, and Bi are the respective vectors of the three primary color components, Inc_R, Inc_G, and Inc_B are the respective brightness control components of the primary colors Red, Green and Blue, and d1, d2 and d3 are predetermined constants, it is preferable to have the control signal generator determine Ro, Go and Bo, indicative of the primary color signals of the brightness controlled output, as Ro=Ri+d1*Inc_R, Go=Gi+d2*Inc_G, Bo=Bi+d3*Inc_B, respectively.